GCD处理任务和runloop的关系

var count = 0
    var timer: Timer? = nil
    func test() {
        let queue = DispatchQueue(label: "aaa")
        queue.async {
            print("start\(Thread.current)")
            queue.asyncAfter(deadline: DispatchTime(uptimeNanoseconds: 1), execute: DispatchWorkItem(block: {
                print("1s后执行异步任务\(Thread.current)")
            }))
            self.perform(#selector(self.perfromTask), with: nil, afterDelay: 2)
            self.timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { _ in
                print("定时任务\(Thread.current)")
                self.count += 1
                if self.count > 10 {
                    self.timer?.invalidate()
                    self.timer = nil
                }
            }
            RunLoop.current.add(self.timer!, forMode: .common)
            RunLoop.current.run()
        }
    }
    
    
    @objc func perfromTask() {
        print("perform 延时任务\(Thread.current)")
    }
    /**
     start<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     perform 延时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     定时任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}
     1s后执行异步任务<NSThread: 0x6000000bc6c0>{number = 7, name = (null)}     //(timer任务会卡住当前线程)
     */